Vaporizer

ABSTRACT

A vaporizer device which works together with an exhaust pipe carrying process exhaust gas. An exhaust duct of the vaporizer device opens into the exhaust pipe. The vaporizer device has a burner comprising an injection device for fuel and air, a combustion chamber, and the exhaust duct. An exhaust gas aftertreatment device is inserted into the exhaust pipe downstream of the junction with the exhaust duct. A method for the operation of such a vaporizer device. According to the invention, a vaporizer device and a method for the operation of such a vaporizer device are provided, and are expanded or improved with respect to the functionality thereof. This is achieved in that an introduction device for the vaporizable liquid is inserted into the exhaust duct. The corresponding method is characterized in that the burner provides sufficient thermal energy, wherein the lower limit thereof is prespecified by the provision of an amount of energy which is sufficient for the vaporization of an amount of vaporizable liquid which is larger than the amount of vaporizable liquid introduced into the exhaust duct.

The invention relates to a vaporizer device which works together with anexhaust pipe carrying process exhaust gas, wherein an exhaust duct ofthe evaporator device opens into said exhaust pipe. The evaporatordevice has a burner comprising an injection device for fuel and air, acombustion chamber, and said exhaust duct. An exhaust gas aftertreatmentdevice is inserted into the exhaust pipe downstream of the junction withthe exhaust duct. The invention also relates to a method for theoperation of such a vaporizer device.

BACKGROUND

Such a vaporizer device is known from DE 10 2004 048 336 A1. Thevaporizer is inserted into the exhaust system of an internal combustionengine, wherein the internal combustion engine exhaust is discharged,and undesired emissions are reduced, by means of said exhaust system. Inaddition, a fuel feed device, an oxidative catalytic converter, and aparticulate filter are arranged in the exhaust system. In order toimprove the introduction of the fuel into the exhaust, a recirculationunit is provided which also functions as a vaporizer, which is connectedto the exhaust system, and to which the fuel feed device is connected,such that the fuel is introduced into the exhaust via or through therecirculation unit. In this case, air can also be supplied to therecirculation device in addition to the fuel, and the resulting mixturein the recirculation device, which works as a burner, can be ignited andburned. Particularly, the amount of fuel can be adjusted for the purposeof regulating the power of the burner. The power of the burner must bedetermined in accordance with the working of the oxidative catalyticconverter in such a manner that it is possible to carry out aregeneration of the particulate filter in all possible operatingconditions.

In addition, vaporizers for an exhaust system of an internal combustionengine are known which directly obtain energy for the purposes ofheating and vaporization from the process exhaust gas. Such vaporizersare not entirely functional in cases where process exhaust gastemperatures are low.

Finally, vaporizers for an exhaust system of an internal combustionengine are known which obtain energy for the purposes of heating andvaporization from electric heating devices. In many such cases, it isdifficult or impossible, or is undesirable due to reasons of efficiency,to make the required amount of electrical energy available.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a vaporizer deviceand/or a method for the operation of such a vaporizer device which isexpanded and/or improved with respect to the function thereof.

The present invention provides an introduction device for a vaporizableliquid is inserted into the exhaust duct of a burner. The correspondingmethod is characterized in that the burner provides sufficient thermalenergy, wherein the lower limit thereof is prespecified by the provisionof an amount of energy which is sufficient for the vaporization of anamount of vaporizable liquid which is larger than the amount ofvaporizable liquid introduced into the exhaust duct.

The configuration according to the invention is characterized in thatthe vaporizer device can be used for any vaporizable liquid. As such, anincombustible liquid, such as an aqueous solution of urea for example,can be vaporized. In the event that the liquid is a flammable fuel, saidfuel is preferably the same fuel which is injected by means of thesupply device of the burner, for example diesel fuel.

However, in principle, it is also possible to use a gaseous fuel for theoperation of the burner, for example natural gas. The separateintroduction of the additional fuel via the introduction device offersthe advantage that a partial volume of the total required fuel issupplied as a “secondary fuel volume” downstream from the burner. Thisis in contrast to the prior art, wherein an amount of fuel, for examplerequired for a process, must be supplied in its entirety via the supplydevice of the burner. This secondary fuel volume is then ultimatelyprepared and/or burned in a completely controlled manner. Thecorresponding possible method variants are explained below together withthe dependent method claims.

One implementation of the invention has an atomizer nozzle in theopening of the introduction device in the exhaust duct, particularly apressure atomizer nozzle or an air atomizing nozzle. In theconfiguration having the pressure atomizer nozzle, the vaporizableliquid is atomized simply by means of the pressure of the vaporizableliquid. As an alternative, however, the introduction device can also bedesigned as an air atomizing nozzle. In this case, the air atomizingnozzle is operated in such a manner that a vaporizable liquid isintroduced into the exhaust duct with a small amount of air. If thevaporizable liquid is fuel, in cases of normal operation of an airatomizing nozzle, 20 L air/min. and 2 cm³/min. of fuel would be suppliedfor the provision of a combustible mixture of fuel and air; however, upto 100 cm³/min of fuel would be supplied by the air atomizing nozzleoperated according to the invention. Such a thick fuel-air mixture isnot primarily combustible.

In a further embodiment, a venturi device is arranged in the exhaustduct near an opening of the introduction device. This effects a rapidmixing of the partial streams of exhaust gas and vaporizable liquidencountering each other.

In a further embodiment of the invention, the burner with the combustionchamber, the exhaust duct, and the introduction device are integratedinto a housing, and the housing is adapted on the exhaust duct.

Consequently, a component is provided which can be installed on variousdifferent exhaust pipes. Here, the housing can be designed in an idealcase in such a manner that the same can be installed on the exhaustsystem, preferably near to the internal combustion engine inapplications involving an internal combustion engine, for exampledirectly behind the exhaust manifold or an exhaust turbo loader of theinternal combustion engine.

In a further embodiment, the exhaust duct projects into the exhaust pipewith at least one port thereof. In this way, a good mixing of theconverging streams of gas is ensured. For this purpose, the exhaust ductis preferably inserted concentrically into the exhaust pipe in such amanner that the port of the exhaust duct is arranged in the direction ofthe process exhaust gas stream, that is, for example, the internalcombustion engine exhaust stream. This configuration achieves anincrease in the velocity of flow of the process exhaust gas, which leadsto a rapid mixing of the gas mixture, the same including the burnerexhaust and the vapor (vaporized liquid), and the process exhaust. Inthis way, ignition of the gas mixture can be prevented if the processexhaust gas contains oxygen.

In order to further inhibit chemical reactions in the region of theinlet, appropriate auxiliary means can be provided which facilitate thesame. Possible examples of such auxiliary means are, for example, aplate or a cone which is arranged before the port of the exhaust duct,wherein the tip of the cone is oriented facing the port of the exhaustduct. This configuration also provides a narrowing of the flow area inthe region of the port, in addition or as an alternative to a furtherincrease in the flow velocity, said narrowing being provided in the formof a venturi device or a venturi nozzle, for example. In other words,the configuration should quench a possible reaction between the processexhaust gas and the burner exhaust, the latter being prepared withvaporizable liquid.

In a further implementation of the invention, a gas feed device opensinto the exhaust duct and carries a process exhaust. In this way,process exhaust gas is fed to the burner exhaust and the vaporizableliquid.

In this way, the burner exhaust is cooled down in a controlled manner(where the feed is configured upstream from the opening of the feedinlet device in the direction of flow), and in such a manner thatsufficient energy is provided for the purpose of vaporizing thevaporizable liquid, although the combustion of the same is prevented (ifthe vaporizable liquid is fuel). However, the feed can also beconfigured in the region of the opening, or downstream from the openingin the direction of flow. A chemical reaction between the vaporizableliquid and the burner exhaust and/or the process exhaust gas can beeither facilitated or inhibited depending on requirements by means ofappropriately selecting the described auxiliary means. Particularly bymeans of influencing the temperature in the region of the feed inletdevice, it is possible to generate substances in a targeted manner bymeans of reactions between the vaporizable liquid and the burnerexhaust, wherein said substances facilitate desired reactions in thedownstream catalytic converters.

In a further embodiment, the exhaust gas aftertreatment device has acatalytic converter which selectively catalytically reduces oxides ofnitrogen, and/or has an NO_(x) storage catalytic converter, and/or anoxidative catalytic converter, and/or at least one particulate filter.Each of the catalytic converters and/or the catalytic converter—particlefilter systems can be operated with the vaporizer device according tothe invention, either alone or in any possible combination thereof, asis explained in greater detail below in the context of the method foroperation. In this case, the scope of the invention also includes aconfiguration wherein the oxidative catalytic converter is amulti-purpose catalytic converter particularly containing vanadium, thesame also being suitable for catalytically facilitating the selectivereduction of nitrogen oxides.

The constructive configurations described above are utilized in areasonable manner for the purpose of implementing the further embodimentof the operating method according to the invention described below. Assuch, the burner is operated in a lambda range from 0.75 to 1.75,preferably at a lambda of 1. In addition, the burner is designed in sucha manner that it can be operated in a power range up to 20 kW,preferably up to 15 kW, and most preferably up to 5 kW. It is one aim ofthe invention to operate the burner at the lower possible power, becauseparticularly the air supply device required for the supply of(combustion-) air can then be designed with a relatively simpleconstruction.

Furthermore, by means of the method according to the invention, and ingeneral, vaporizable liquid (optionally along with the direct additionof a partial volume of the process exhaust gas) is vaporized by means ofthe burner exhaust gas, and is directed into the exhaust aftertreatmentdevice together with the burner exhaust gas and the entire volume of theprocess exhaust gas, for the purpose of inciting the intended reactionsat that point. For applications involving internal combustion engineswhich are operated with diesel fuel, NH₃ which is generated from avaporized solution of urea effects a chemical reaction in an SCRcatalytic converter wherein the nitrogen oxide and the NH₃ are convertedto nitrogen and water vapor. In the event that, also for applicationsinvolving internal combustion engines which are operated with dieselfuel, the vaporizable liquid is a combustible fuel, the same is fed toan oxidative catalytic converter and a downstream particulate filter viathe exhaust pipe together with the burner exhaust and the processexhaust, and is oxidized in the oxidative catalytic converter and/or ina catalyst-coated particulate filter. A particular advantage of thisconfiguration is that the oxidation reaction therefore occurs only inthe oxidative catalytic converter, and as a result, the temperaturesrequired for the regeneration of the particulate filter are onlygenerated at that point in the system. If the injected fuel were to beignited at the point of introduction in the exhaust duct, as takes placein the system described in the prior art, this would be associated witha higher thermal load on the entire exhaust system, and significant heatloss would have to be compensated for by a higher quantity of fuel. Atemperature of up to 650° C., for example, is generated by the oxidationof the vaporized fuel in the oxidative catalytic converter, and the sameis required for the regeneration of particulate filters.

In a further embodiment of the invention, different vaporizable liquids,particularly fuel and aqueous urea solution, can be introduced into theexhaust duct via one or multiple introduction devices.

In cases where only one introduction device is included, the supply ofvaporizable liquid is controlled in an alternating manner via acorresponding switching device, whereas no switching device is necessaryin cases where two introduction devices are included. Such a case alsonormally includes the alternating supply of vaporizable liquid. Thisalternating supply can be used advantageously, for example, if theoxidative catalytic converter is a multi-purpose catalytic converterparticularly containing vanadium, the same also being suitable forfacilitating the catalytic reduction of NO_(x). In this case, theoxidative catalytic converter is alternatingly used for variousdifferent functions. However, it is also certainly possible to includean oxidative catalytic converter and a separate catalytic converterwhich effects a selective catalytic reduction of NO_(x).

In an further embodiment of the method, a partial volume of the totalvolume of combustible fuel, the same being introduced as the vaporizableliquid and then vaporized, is oxidized within the exhaust duct and/or inthe place where the same is brought together with the process exhaust,releasing heat. In this way, the total thermal energy provision isincreased, coincident with burner performance adjusted to a minimalsetting, to such a degree that the startup of a catalytic converter isensured. In order to initiate the activity thereof, that is, in order tostart a catalytic reaction of the introduced, vaporized fuel, anoxidative catalytic converter must achieve a prespecified minimumtemperature, for example 300° C. This temperature is achieved by meansof the total sum of energy from the burner and the energy generated bythe combusted partial volume.

In a further embodiment, the oxidized partial volume of the total volumeof vaporized fuel is kept at least essentially constant, independent ofthe total volume of vaporized fuel. This embodiment also includes thediscontinuation of the partial conversion of the fuel once a thresholdvolume of the partially converted fuel has been reached, at which pointthe total fuel volume is vaporized in its entirety. These differingeffects are achieved by strict control of the combustion mixture ratioin the burner and/or by strict control, in a configuration utilizing anair atomizing nozzle, of the amount of atomizing air supplied to the airatomizing nozzle.

Additional influencing variables are the location of the attachment ofthe opening of the introduction device, and the feed of a partial volumeof process exhaust gas (for the purpose of cooling the burner exhaustand consequently the vaporizable liquid), likewise with respect to thelocation of said feed.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantageous embodiments of the invention are described belowwith reference to the illustrations, which depict an embodiment,wherein:

FIG. 1 shows a first embodiment of the vaporizer device which workstogether with an exhaust pipe,

FIG. 2 shows a second embodiment of the vaporizer device which workstogether with an exhaust pipe, and

FIG. 3 shows a third embodiment of the vaporizer device which workstogether with an exhaust pipe.

DETAILED DESCRIPTION

For all embodiments, the vaporizer device has a housing 1, in which aburner 2, a combustion chamber 3, an exhaust duct 4, and an introductiondevice 5 for a vaporizable liquid are integrated. Here, the housing 1,likewise in all embodiments, is connected to an exhaust pipe 6 in such amanner that the exhaust duct 4, having a port 7, is insertedconcentrically into the exhaust pipe 6, and the port 7 is arranged inthe direction of the flow of the process exhaust gas flowing through theexhaust pipe 6.

The burner 2 has a supply device 8 a for a gaseous or liquid combustiblefuel, as well as a supply device 8 b for air. The fuel and the air aremixed with each other in a suitable manner and introduced into thecombustion chamber 3, for example via an air atomizing nozzle 9. Themixture is then combusted in the combustion chamber 3. For this purpose,the mixture in the burner 2 and/or the combustion chamber 3 is ignitedin a suitable manner. In order to keep heat loss low, the combustionchamber 3 is inserted into the housing 1 and insulated as extensively aspossible. The combustion chamber 3 has an exhaust opening 10 throughwhich the burner exhaust enters into the exhaust duct 4, then flowsalong the exhaust duct 4 to the port 7. At this point, said burnerexhaust mixes with the process exhaust gas flowing in the exhaust pipe6, which in the embodiment is the exhaust of an internal combustionengine. The mixture of burner exhaust and air is adjusted in such amanner that the oxidation reaction is largely completed in the region ofthe exhaust opening 10 of the combustion chamber 3, and as a result, aheated stream of exhaust gas flows into the exhaust duct 4. Theintroduction device 5 opens with an opening 11 into the exhaust duct 4,preferably concentrically with respect to the exhaust duct 4. Anatomizer nozzle 16 is arranged at the location of the opening 11, andvaporizable liquid supplied via the introduction device 5 is finelyatomized by means of the same. The vaporizable liquid introduced in thismanner is consequently heated and vaporized. A venturi device 12 a isinserted into the exhaust duct 4 in the region of the opening 11. Theventuri device 12 a effects an additional mixing of the vaporizableliquid with the exhaust gas. A quenching device 13 is arranged in theregion of the port 7, wherein said quenching device 13 is designed as abaffle plate in the embodiment and functions to mix the exhaust gases,the same flowing out of the port 7 and being mixed with the vaporizedvaporizable liquid, with the process exhaust gas. At the same time, thequenching device 13 can be used to prevent ignition of the full mixtureformed at this point. A venturi device 12 b is installed in the exhaustpipe 6 in the region of the port 7 and/or the quenching device 13 forthe purpose of increasing the flow velocity of the process exhaust gas.

The full mixture formed in the described manner is then fed to anexhaust gas aftertreatment device 17, shown schematically, which has acatalytic converter 18 which catalytically reduces nitrogen oxides,and/or has an NO_(x) storage catalytic converter, and/or an oxidativecatalytic converter, and has a particulate filter 19. A catalyticconverter 20, shown schematically, can also be provided in exhaust duct4.

The embodiment according to FIG. 2 differs from the embodiment accordingto FIG. 1 in that additionally a gas feed device 14 in the form ofdrilled holes arranged on the periphery of the exhaust duct 4 andopening approximately in the center of the venturi device 12 a isarranged in the region of the venturi device 12 a. A partial volume ofthe process exhaust gas is inserted into the exhaust duct 4 through thisgas feed device 14. In addition, no venturi device 12 b is installed inthe region of the port 7 in this embodiment.

The embodiment according to FIG. 3 differs from the embodiment accordingto FIG. 2 in that here the gas feed device 14 is inserted into theexhaust duct 4 in the region which is downstream from the venturi device12 a.

REFERENCE NUMBERS

-   1 Housing-   2 Burner-   3 Combustion chamber-   4 Exhaust duct-   5 Introduction device-   6 Exhaust pipe-   7 Port-   8 a, 8 b Supply device-   9 Air atomizing nozzle-   10 Exhaust port-   11 Opening-   12 a, 12 b Venturi device-   13 Quenching device-   14 Gas feed device-   16 Nozzle-   17 Aftertreatment device-   18 Catalytic converter-   19 Filter-   20 Catalytic converter

1-28. (canceled)
 29. A vaporizer device working together with an exhaustpipe carrying a process exhaust gas, the vaporizer device comprising: aburner with a supply device for combustible fuel and air, a combustionchamber, and an exhaust duct opening into the exhaust pipe; an exhaustgas aftertreatment device in the exhaust pipe downstream from theopening of the exhaust duct; and an introducer for a vaporizable liquidin the exhaust duct.
 30. The vaporizer device as recited in claim 29herein the combustible fuel is a gaseous or liquid fuel.
 31. Thevaporizer device as recited in claim 29 wherein the vaporizable liquidis an aqueous solution of urea or a liquid combustible fuel.
 32. Thevaporizer device as recited in claim 29 wherein the introducer has anatomizer nozzle.
 33. The vaporizer device as recited in claim 29 whereina venturi device is arranged in the exhaust duct in a region of anopening of the introducer.
 34. The vaporizer device as recited in claim29 further comprising a housing, the burner, the exhaust duct, and theintroduction device being integrated into the housing, and the housingis adapted on the exhaust pipe.
 35. The vaporizer device as recited inclaim 29 wherein the exhaust duct projects with a port at the openinginto the exhaust pipe.
 36. The vaporizer device as recited in claim 35wherein the exhaust duct is concentrically inserted into the exhaustpipe in such a manner that the port of the exhaust duct is arranged in adirection of the process exhaust gas stream.
 37. The vaporizer device asrecited in claim 35 further comprising a quenching device and/or aventuri device in a region of the port.
 38. The vaporizer device asrecited in claim 29 further comprising a gas feed device carrying aprocess exhaust gas and opening into the exhaust duct.
 39. The vaporizerdevice as recited in claim 29 wherein the exhaust gas aftertreatmentdevice has an oxidative catalytic converter and a particulate filter.40. The vaporizer device as recited in claim 29 wherein the exhaust gasaftertreatment device has a catalytic converter which selectivelycatalytically reduces nitrogen oxides.
 41. The vaporizer device asrecited in claim 29 wherein the exhaust gas aftertreatment device has anNO_(x) storage catalytic converter.
 42. A method for the operation of avaporizer device working together with an exhaust pipe carrying aprocess exhaust gas, an exhaust duct of the vaporizer device openinginto the exhaust pipe, the vaporizer device has a burner with a supplydevice for combustible fuel and air, as well as a combustion chamber,and the exhaust duct, an exhaust gas aftertreatment device beinginserted into the exhaust pipe downstream from the opening of theexhaust duct, the method comprising: providing thermal energy via theburner, a lower limit of the thermal energy being prespecified by aprovision of an amount of energy sufficient for vaporization of anamount of vaporizable liquid which is larger than the amount ofvaporizable liquid introduced into the exhaust duct via an introducer.43. The method as recited in claim 42 wherein various differentvaporizable liquids are introduced into the exhaust duct via theintroducer.
 44. The method as recited in claim 42 wherein the burnerprovides additional thermal energy heating the process exhaust gas to aprespecified temperature.
 45. The method as recited in claim 42 whereinthe burner provides energy sufficient to vaporize an aqueous solution ofurea introduced as the vaporizable liquid, and to heat a catalyticconverter to an operating temperature thereof, the catalytic converterbeing a part of the exhaust gas aftertreatment device and selectivelycatalytically reducing nitrogen oxides present in the system.
 46. Themethod as recited in claim 42 wherein generation of NH₃ from theintroduced urea solution is facilitated by a catalytic converterinstalled in the exhaust duct.
 47. The method as recited in claim 42wherein the burner provides energy sufficient at least to vaporize aliquid fuel introduced as the vaporizable liquid, and to heat an NO_(x)storage catalytic converter present as a part of the exhaust gasaftertreatment device.
 48. The method as recited in claim 42 wherein theburner provides energy sufficient at least to vaporize a liquid fuelintroduced as the vaporizable liquid, and to heat an oxidative catalyticconverter present as a part of the exhaust gas aftertreatment device toan operating temperature required for the catalytic oxidation of thefuel.
 49. The method as recited in claim 48 wherein the heating processis facilitated by a catalytic converter installed in the exhaust duct.50. The method as recited in claim 48 wherein the oxidative catalyticconverter is a multi-purpose catalytic converter containing vanadium andsuitable for facilitating the selective catalytic reduction of NO_(x).51. The method as recited in claim 42 wherein a partial volume of atotal volume of combustible fuel is oxidized inside the exhaust ductand/or a location where the fuel is brought together with the processexhaust gas, releasing heat.
 52. The method as recited in claim 51wherein a thermal energy of the partial volume of oxidized fuel is heldat least approximately constant independent of the total volume of fuel.53. The method as recited in claim 51 wherein a total volume of fuel isvaporized once a threshold volume is exceeded.
 54. The method as recitedin claim 42 wherein the process exhaust gas is introduced into theexhaust duct by a gas feed device.
 55. The method as recited in claim 42wherein desired chemical reactions are facilitated by influencing atemperature and composition of a gas at a location of injection o ftehvaporizable liquid.
 56. The method as recited in claim 55 wherein acatalytic converter is inserted in the exhaust duct for the purpose offacilitating the desired reaction.